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Creating a Lossless infrastructure on the OS6900/OS10K in support of FCoE/Fiber-Channel Storage

Creating a Lossless infrastructure on the OS6900/OS10K in support of FCoE/Fiber-Channel Storage

Fiber-Channel Storage systems are inherently Lossless. In support of Converged Networks (FCoE), a lossless infrastructue must be created over traditional Lossy ethernet fabrics.
TCP inherently supports a lossless mode via retransmissions and acknowledgements. Applications using UDP will have to implement their own recovery mechanisms.
FCoE as it runs over plain Ethernet will have to depend on Priority Flow Control, Enhanced Transmission Selection & DataCenter Bridging Exchange Protocol to create it.
If you want to learn more, go the IEEE webpage :

The OmniSwitch Series of Switches support DataCenter bridging protocols via the application of Profiles at a port Level.
In essence, The profiles are pre-defined templates which enable a particular priority for Lossless behavior ( at the ingress) ; Provide a bandwidth guarantee for a class of traffic at the egress
and enable auto-configuration of local/peers via LLDP/DCBx negotiations. Both the earlier CEE and current IEEE modes of DCBx are supported.

By Setting PFC and ETS Willing FLAGS accordingly , it is possible to steer the negotiations across the entire fabric to be consistent.

In most cases, the Servers are Willing and configure themselves to send FCOE traffic at a particular 802.1p priority based on LLDP negotiation with the Switch.

Lets take a predefined Template : DCP-8. DCP-8 is the default profile on all ports on bootup. It classifies traffic into 8 different traffic classes and schedules traffic based on Strict-Priority.
However, All traffic classes are non-Lossless. Hence they could be dropped when there is a congestion .

Now that the Custom Profile is created, We need to apply it to all the Edge-facing ports on the Core.
It is also required to Configure the Core to be non-willing, So that it does not change its PFC/ETS behavior based on LLDP packets received.
The Edge should remain willing. This ensures that the configuration is applied at a central place at the Core and pushed downwards to the edges.

As PFC/ETS is required to be configured at a per-link level, we have to do the same at the edge-port connected to the server. In addition, we have to configure the LLDP Application TLV.
This is information which the Server acts upon to configure Lossless behavior and start the FCOE discovery process.